[unreadable] Cardiac arrest remains the number one killer in the developed world, despite the introduction of [unreadable] cardiopulmonary resuscitation (CPR) and defibrillation over 50 years ago. In the U.S. alone, cardiac arrest afflicts over 300,000 people each year, with less than 10% of patients surviving the event despite often extensive resuscitative efforts. The survival benefit of well-performed CPR is well documented in animal studies and several subjective human observational reports, but little objective data exists regarding CPR quality during actual cardiac arrest. Recent studies have challenged the notion that CPR is uniformly performed according to established consensus guidelines. In addition, simulation studies have suggested that audio feedback on CPR performance may improve quality. Work from our group and others using novel monitoring technology has recently shown that the quality of multiple CPR parameters is inconsistent and often falls short of guideline recommendations, even when performed by well-trained medical personnel. We hypothesize that resuscitation performance is limited by a variety of human factors including poor establishment of team leadership at the arrest and poor attention to task performance. We further hypothesize that real-time automatic monitoring of CPR with frequent audio and visual feedback to rescuers will improve the quality of CPR performance. We will measure human factor parameters such as team leadership and task assignment during in-hospital cardiac arrests via direct observation by trained investigators. By careful study of the human factors of resuscitation team function, we will be able to impact CPR education and training by targeting deficiencies leading to poor performance. Using monitor/defibrillators with specialized CPR sensors and audio feedback prompts, we will assay whether CPR performance is improved by feedback, and will then determine in patients with improved CPR quality, whether an improvement in survival is achieved. Using this exciting new monitoring and feedback modality, we hope to establish a standard for optimal CPR performance methodology that would broadly impact the health and survival of patients who suffer from cardiac arrest both in the hospital and the community.